Various types of storage devices are available to store data for electronic devices. Examples of storage devices include tape-based storage devices, disk-based storage devices, integrated circuit (IC) storage devices, and others.
In a tape-based storage device, data is stored on plural data tracks of a storage tape, where the data tracks extend generally longitudinally along the storage tape. The reading and recording of data in the data tracks is accomplished by using tape heads, which typically include magnetic read/write heads for reading/recording data on magnetic storage tapes.
The storage tape is moved longitudinally with respect to the tape head as the recording operation or read operation proceeds. When reading from or writing to a storage tape, accurate lateral positioning of the tape head is desirable. To achieve accurate lateral positioning of the tape head, servo bands (or servo tracks) are recorded onto the storage tape. The servo bands contain servo patterns that are detectable by the tape head during read/write operations for determining the lateral position of the tape head with respect to the storage tape.
One approach of deriving lateral position information from a servo band is a timing-based servo approach. Typically, in this approach, the servo patterns recorded onto the servo band of the storage tape include servo “stripes” that are recorded with servo write elements on a tape head. In many conventional tape-based storage devices, a tape head includes two servo write elements that have different angular orientations with respect to the longitudinal axis of the linear tape to form a pair of servo stripes having different angular orientations (also referred to as azimuthal orientations). Repeating patterns of these servo stripes are recorded onto the storage tape. During a write or read operation, the tape head reads the servo stripes and derives various distance information (corresponding to distances between various pairs of servo stripes) to determine the lateral position of the tape head over the storage tape.
With a tape head that has just two servo write elements, the distances between successive pairs of servo stripes can vary if the tape speed varies during a servo write operation. Variations in tape speed would cause errors in the signals generated from reading the servo stripes for determining the lateral position of the tape head over the storage tape. Such errors would cause errors in the lateral position of read/write elements of the tape head with respect to the storage tape. Improper lateral positioning of read/write elements over a data track of the storage tape can cause errors to occur during data read or write operations. As track densities continue to increase on storage tapes, these errors induced by tape speed variations can cause increased likelihood of data errors occurring during data read or write operations.